ANKARA - The opposition Syrian National Council has failed to overcome internal divisions and is not up to the challenge of overthrowing President Bashar al-Assad, a prominent former member of the group has said.

Assad, in a rare television interview, said he would need more time to defeat the rebels and dismissed talk of a Western-imposed buffer zone on Syrian territory as unrealistic.

Basma Kodmani, who resigned from the Syrian National Council this week, said the group was not doing enough to back the increasingly violent 17-month-old revolt against the government in Damascus and needed to be replaced by a new political authority.

"My sense was that the SNC was not up to facing the increasing challenges on the ground and was not up to the performance I would have liked it to be," she told Reuters in a telephone interview from Paris on Wednesday.

Kodmani, one of the few women in the SNC, headed its foreign affairs bureau. The SNC was formed in Istanbul last year to guide a democratic transition if Assad fell but has been accused by some of being dominated by Islamists.

"The groups inside the council did not all behave as one in promoting one national project," Kodmani said. "Some have given too much attention to their own partisan agendas, some to their personal agendas sometimes. That resulted in a major weakness in connecting closely with the groups on the ground and providing the needed support in all forms."

In Syria, opposition activists reported air and ground bombardment by government forces in eastern neighbourhoods of Damascus, which prompted thousands to flee the area.

The opposition Syrian Observatory for Human Rights said around 100 people were killed on Wednesday, 29 of them government soldiers. So far the war has claimed more than 18,000 lives, according to the United Nations.

Turkey, already host to tens of thousands of refugees fleeing the fighting, urged the United Nations to protect displaced Syrians inside their country.

Ankara fears a mass influx such as the flight of half a million Iraqi Kurds into Turkey after the 1991 Gulf War, and has floated the idea of a "safe zone" under foreign protection within Syria for civilians fleeing intensifying violence.

"We expect the United Nations to engage on the topic of protecting refugees inside Syria and if possible sheltering them in camps there," Foreign Minister Ahmet Davutoglu said.

France supports Turkey's call for a safe zone in Syria, and pressure for action increased after the U.N. refugee agency said that Syria's exodus was accelerating. Up to 200,000 people could settle in Turkey if the conflict worsens, the UNHCR said.